Power steering apparatus of watercraft with propeller

ABSTRACT

In a power steering apparatus of a watercraft  1  with propeller having a steering handle provided in a bow end of a hull, a propeller provided in a stern end of the hull, and a steering assist apparatus interposed in a steering force transmission path transmitting a steering force applied to the steering handle to the propeller, the steering assist apparatus is arranged in an intermediate portion of a steering cable constructing a propelling force transmission path.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a power steering apparatus of a watercraft with propeller such as an outboard motor, an inboard outboard motor and the like.

2. Description of the Related Art

In a power steering apparatus of a watercraft with propeller, there is a structure having a steering handle provided in a bow end of a hull, a propeller provided in a stern end of the hull, and a steering assist apparatus interposed in a steering force transmission path transmitting a steering force applied to the steering handle to the propeller, as described in Japanese Patent Publication (Laid-Open) No. 2004-231108 (patent publication 1). It assists a manual steering force applied by a watercraft steering person to the steering handle on the basis of a steering assist force generated by an electric assist motor of a steering assist apparatus (or an electric assist pump of a hydraulic power steering apparatus).

In the conventional power steering apparatus of the watercraft with propeller, the steering assist apparatus including the electric assist motor is arranged in the vicinity of the steering handle in an inner portion in the bow end of the hull, or is arranged in the vicinity of the propeller in an inner portion of the stern end of the hull.

However, the inner portion in the bow end in the vicinity of the steering handle has little extra space due to the arrangement of the steering assist apparatus.

Further, the inner portion in the stern end in the vicinity of the propeller has little space which avoids an interference between the steering assist apparatus and a tilt-up propeller, and may be generally undesirable as a waterproof environment with respect to the steering assist apparatus.

SUMMARY OF THE INVENTION

An object of the present invention is to improve an arrangement layout characteristic and a waterproof environment characteristic for a steering assist apparatus, in a power steering apparatus of a watercraft with propeller.

The present invention relates to a power steering apparatus of a watercraft with propeller comprising: a steering handle provided in a bow end of a hull; a propeller provided in a stern end of the hull; and a steering assist apparatus interposed in a steering force transmission path transmitting a steering force applied to the steering handle to the propeller. The steering assist apparatus is arranged in an intermediate portion of a steering cable constructing a propelling force transmission path.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood from the detailed description given below and from the accompanying drawings which should not be taken to be a limitation on the invention, but are for explanation and understanding only.

The drawings:

FIG. 1 is a schematic view showing a power steering apparatus of a watercraft with propeller in accordance with an embodiment 1;

FIG. 2 is a schematic view showing a steering assist apparatus in FIG. 1;

FIG. 3 is a schematic view showing a power steering apparatus of a watercraft with propeller in accordance with an embodiment 2;

FIG. 4 is a schematic view showing a steering assist apparatus in FIG. 3;

FIG. 5 is a cross sectional view showing a screw reaction force suppressing apparatus along a line V-V in FIG. 4; and

FIG. 6A to 6C are schematic views showing a motion of the screw reaction force suppressing apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 (FIGS. 1 and 2)

A watercraft 1 shown in FIG. 1 has a steering handle 10 provided in a bow end of a hull 2, an outboard motor 20 serving as a propeller provided in a stern end of the hull 2, and a steering cable 30 serving as a steering force transmission path transmitting a steering force applied to the steering handle 10 to the outboard motor 20. The steering cable 30 consists of a steering handle side steering cable 30A and an outboard side steering cable 30B. The steering cable 30 is extended within an outer tube 31 installed in the stern end from the bow end in an inner portion of the hull 2.

The steering handle 10 is installed in a control seat in the bow end of the hull 2. A pinion 12 fixed to a handle shaft 11 of the steering handle 10 is engaged with a rack 13, and the rack 13 is coupled to one end of the steering cable 30 (30A). The steering handle 10 is rotated leftward or rightward on the basis of an application of a steering force (a steering torque), whereby the steering cable 30 is pushed and pulled via an engagement between the pinion 12 and the rack 13.

The outboard motor 20 is provided with a screw 22 in a propelling unit 21, and is structured such as to have an engine (not shown) mounted on the propelling unit 21, and a swivel bracket 23 and a clamp bracket 24. The propelling unit 21 is pivoted to the swivel bracket 23 via a steering shaft 23A (not shown) so as to oscillate in a horizontal direction and be capable of steering, and the swivel bracket 23 is pivoted to the clamp bracket 24 so as to be tiltable up and down in a vertical direction via a tilt shaft 24A (not shown). The outboard motor 20 is attached to a stern plate of the hull 2 by the clamp bracket 24, transmits an output of the engine to the screw 22, and makes the hull 2 movable forward and backward. The outboard motor 20 couples one end of the steering cable 30 (30B) to a steering arm 21A firmly attached to the propelling unit 21.

In the watercraft 1, a steering assist apparatus 40 for constructing a power steering apparatus 3 assisting a steering force applied by a watercraft steering person to the steering handle 10 is interposed in the steering cable 30. The steering assist apparatus 40 is interposed between the first cable 30A and the second cable 30B, corresponding to an intermediate portion of the steering cable 30, and is arranged in a gunwale side of the center of the hull (a port side or a starboard side of the center between the bow and the stern in an inner portion of the hull 2) in the present embodiment.

The steering assist apparatus 40 is arranged within a gear case 41 fixed to the hull 2, as shown in FIG. 2. The steering assist apparatus 40 coaxially couples an input shaft 42 and an output shaft 43 via a torsion bar (not shown), and pivots the input shaft 42 and the output shaft 43 to the gear case 41. A rack 45 coupled to the other end of the first cable 30A is engaged with a pinion 44 fixed to the input shaft 42, and the rack 45 is slidably supported to the gear case 41. A rack 47 coupled to the other end of the second cable 30B is engaged with a pinion 46 fixed to the output shaft 43, and the rack 47 is slidably supported to the gear case 41. Accordingly, if the steering handle 10 is rotated to the left or the right on the basis of an application of a steering force, the first cable 30A is pushed or pulled so as to cause a linear motion of the rack 45, the input shaft 42 and the output shaft 43 are rotated on the basis of the engagement between the rack 45 and the pinion 44, and the rack 47 and the second cable 30B are pushed and pulled on the basis of the engagement between the pinion 46 and the rack 47 in the output shaft 43. As a result, the propelling unit 21 coupled by the second cable 30B and the steering arm 21A is steered leftward or rightward.

The steering assist apparatus 40 is structured such that a torque sensor 48 is interposed between the input shaft 42 and the output shaft 43 within the gear case 41. The torque sensor 48 detects a steering direction and a steering torque applied by the watercraft steering person to the steering handle 10.

The steering assist apparatus 40 is structured such that an electric assist motor 50 is arranged within the gear case 41, and a worm 51 provided in an output shaft of the assist motor 50 is engaged with a worm wheel 52 provided in the output shaft 43.

The steering assist apparatus 40 is structured such that a control unit 60 controlling the assist motor 50 is arranged within the gear case 41. The control unit 60 loads a detection signal of the torque sensor 48, and a detection signal of a watercraft speed sensor 61 installed in the propelling unit 21 of the outboard motor 20, decides a driving direction and a driving current of the assist motor 50 from a predetermined assist map, and applies a motor torque of the assist motor 50 which becomes a suitable steering assist force corresponding to the watercraft speed, the steering direction and the motor torque to the output shaft 43 via the worm 51 and worm wheel 52.

The steering assist apparatus 40 is provided with a screw reaction force suppressing apparatus 70 in the output shaft 43. The screw reaction force suppressing apparatus 70 sets up against an inverse input applied to the second cable 30B from the side of the propelling unit 21 via the steering arm 21 on the basis of the rotational reaction force of the screw 22 of the outboard motor 20. The screw reaction force suppressing apparatus 70 is constructed, for example, by a braking means applying a constant braking force to the output shaft 43, holds back the rotation of the output shaft 43 against the mentioned-above inverse input applied to the second cable 30B, and allows the rotation of the output shaft 43 caused by the manual steering torque applied to the steering cable 30, or the motor torque of the assist motor 50. The braking means constructing the screw reaction force suppressing apparatus 70 can be structured such that it can easily regulate a braking force on the basis of being provided in a free end of the output shaft 43 within the gear case 41.

In accordance with the present embodiment, the following operations and effects can be achieved.

(a) The steering assist apparatus 40 is arranged in the intermediate portion of the steering cable 30 constructing the propelling force transmission path. Accordingly, the steering assist apparatus 40 can be arranged in the extra space in the inner portion of the hull 2.

(b) Since the steering assist apparatus 40 is arranged in the intermediate portion of the steering cable 30, the steering assist apparatus 40 has a freedom in arrangement by regulating a length of the steering cable 30.

(c) On the basis of the item (b), the steering assist apparatus 40 can be arranged in the vicinity of the battery provided in the inner portion of the hull 2, and it is possible to reduce an electrical loss.

(d) The steering assist apparatus 40 can be isolated from the bow and the stern of the hull 2, and can be arranged in a place having a good waterproof environment.

(e) The steering assist apparatus 40 is arranged in the watercraft board of the center of the hull 2. Accordingly, it is possible to securely achieve the items (a) to (d).

(f) The torque sensor 48 detecting the steering torque applied to the steering handle 10 is arranged within the gear case 41 constructing the steering assist apparatus 40. Accordingly, it is possible to simply improve the waterproof environment characteristic for the torque sensor 48 in addition to the steering assist apparatus 40. Further, the torque sensor 48 can be added to the steering assist apparatus 40, and it is possible to improve an attaching characteristic of the torque sensor 48. Further, a control unit 60 controlling the steering assist apparatus 40 is arranged within the gear case 41 constructing the steering assist apparatus 40. Accordingly, it is possible to simply improve the waterproof environment characteristic for the control unit 60, in addition to the steering assist apparatus 40. Further, the control unit 60 can be added to the steering assist apparatus 40, and it is possible to improve an attaching characteristic of the control unit 60.

(g) The output side of the steering assist apparatus 40 is provided with the screw reaction force suppressing apparatus 70 setting up against the inverse input applied to the steering cable 30 from the side of the outboard motor 20 on the basis of the rotational reaction force of the screw 22 provided in the outboard motor 20. It is possible to stop the gyro effect that the outboard motor 20 is going to be steered on the basis of the rotational reaction force of the screw 22, by means of the screw reaction force suppressing apparatus 70, and it is possible to maintain the traveling direction of the hull 2 even if the operator loses hold of the steering handle 10, for example, thereby maintaining a linear moving characteristic thereof. It is not necessary to apply the steering force setting up against the inverse input applied to the steering cable 30 on the basis of the rotational reaction force of the screw 22 to the steering handle 10, and it is not necessary as a result for the steering assist apparatus 40 to generate the steering assist force corresponding to the steering force. Therefore, it is possible to avoid a unnecessary power consumption of the electric assist motor 50 (or the hydraulic cylinder) of the steering assist apparatus 40.

Embodiment 2 (FIGS. 3 to 6C)

A difference between a power steering apparatus 3 of a watercraft 1 in accordance with an embodiment 2 shown in FIGS. 3 and 4 the embodiment 1 is that a screw reaction force suppressing apparatus 80 is provided between the worm wheel 52 and the rack 47 on the output shaft 43 of the steering assist apparatus 40.

The screw reaction force suppressing apparatus 80 has a retainer 81A serving as an input side member 81 to which the motor torque of the electric assist motor 50 is input, as shown in FIG. 5, and fixedly couples the input side member 81 to the output shaft 43. The screw reaction force suppressing apparatus 80 has an output side member 82 from which the motor torque of the assist motor 50 is output, fixedly coupling the pinion 46 to the output side member 82, and engages the pinion 46 with the rack 47. The screw reaction force suppressing apparatus 80 has an outer ring 83A serving as a static side member 83 in which a rotation is constrained, and fixedly couples the static side member 83A to the gear case 41. The screw reaction force suppressing apparatus 80 has a lock means 84 which is provided between the outer ring 83A of the static side member 83 and the output side member 82, and locks the output side member 82 and the static side member 83 with respect to an inverse input torque from the output side member 82 (a torque given from the inverse input applied to the second cable 30B on the basis of the rotational reaction force of the screw 22 of the outboard motor 20 mentioned above to the output side member 82 via the rack 47 and the pinion 46). The lock means 84 is constructed by a pair of rollers 84A and 84A provided in a gap of the outer ring 83A and the output side member 82. An N-shaped leaf spring 84B serving as an elastic member applying a force isolating the rollers 84A from each other is interposed between a pair of rollers 84A and 84A. The screw reaction force suppressing apparatus 80 has an unlocking means 85 that is provided in the input side member 81 and unlocks a lock state by the lock means 84 with respect to the motor torque from the input side member 81. The unlocking means 85 is constructed by a column portion 81B of the retainer 81A. The screw reaction force suppressing apparatus 80 has a torque transmitting means 86 which is provided between the input side member 81 and the output side member 82, and transmits the motor torque from the input side member 81 to the output side member 82 during unlocking of the lock state by the lock means 84. The torque transmitting means 86 is constructed by a pin 81C of the retainer 81A. The pin 81C is inserted to a pin hole 82A of the output side member 82, and an inner diameter of the pin hole 82A is made slightly larger than an outer diameter of the pin 81C.

In the screw reaction force suppressing apparatus 80, in a state in which the watercraft steering person loses hold of the steering handle 10 and does not apply a manual steering force, and the motor torque of the assist motor 50 is not applied to the retainer 81A of the input side member 81, the inverse input caused by the rotational reaction force of the screw 22 of the outboard motor 20 is applied to the second cable 30B. As a result, even if the inverse input torque via the rack 47 and the pinion 46 to which the second cable 30B is coupled is applied to the output side member 82, the roller 84A of the lock means 84 interposed between the output side member 82 and the outer ring 83A of the static side member 83 is engaged with a wedge gap between the output side member 82 and the outer ring 83A of the static side member 83 by the leaf spring 84B so as to be locked, as shown in FIG. 6A. Accordingly, the second cable 30B is set incapable of being pushed and pulled and does not steer the propelling unit 21, thereby maintaining a traveling direction of the hull 2 before losing hold of the steering handle 10.

If the manual steering force is applied to the steering handle 10 as shown in FIG. 6B from the lock state of the output side member 82 and the static side member 83 in FIG. 6A, and the steering torque applied to the steering handle 10, and the motor torque of the assist motor 50 controlled by the control unit 60 are applied to the retainer 81A of the input side member 81, the column portion 81B of the retainer 81A serving as the unlocking means 85 comes into collision with one roller 84A positioned in a rear side of the rotating direction, and presses the roller 84A forward in the rotating direction against the leaf spring 84B. Accordingly, the roller 84A engaging by wedge between the output side member 82 and the outer ring 83A of the static side member 83 breaks away from the wedge gap, and the lock state of the output side member 82 is canceled. Accordingly, the output side member 82 becomes rotatable.

If the retainer 81A of the input side member 81 is further rotated from FIG. 6B, the pin 81C of the input side member 81 comes into collision with an inner diameter surface of the pin hole 82A of the output side member 82 as shown in FIG. 6C, and the torque of the input side member 81 is transmitted to the output side member 82 via the pin 81C, and rotates the output side member 82. Accordingly, the pinion 46 fixed to the output side member 82 is rotated, and the rack 47 and the second cable 13B are pushed and pulled via the engagement between the pinion 46 and the rack 47, thereby steering the propelling unit 21 coupled by the second cable 31B and the steering arm 21A.

In accordance with the present embodiment, the following operation and effect can be achieved, in addition to the operations and effects in the items (a) to (f) of the embodiment 1.

By means of the screw reaction force suppressing apparatus 80, it is possible to stop the gyro effect that the outboard motor 20 is going to be steered on the basis of the rotational reaction force of the screw 22, and it is possible to maintain the traveling direction of the hull 2 even if the operator loses hold of the steering handle 10, for example, thereby maintaining a linear traveling characteristic thereof. It is not necessary to apply the steering force setting up against the inverse input applied to the steering cable 30 on the basis of the rotational reaction force of the screw 22 to the steering handle 10, and it is not necessary as a result for the steering assist apparatus 40 to generate the steering assist force corresponding to the steering force. Therefore, it is possible to avoid the unnecessary power consumption of the electric assist motor 50 (or the hydraulic cylinder) of the steering assist apparatus 40.

As heretofore explained, embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configurations of the present invention are not limited to the illustrated embodiments but those having a modification of the design within the range of the presently claimed invention are also included in the present invention.

Although the invention has been illustrated and described with respect to several exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made to the present invention without departing from the spirit and scope thereof. Therefore, the present invention should not be understood as limited to the specific embodiment set out above, but should be understood to include all possible embodiments which can be encompassed within a scope of equivalents thereof with respect to the features set out in the appended claims. 

1. A power steering apparatus of a watercraft with propeller comprising: a steering handle provided in a bow end of a hull; a propeller provided in a stern end of the hull; and a steering assist apparatus interposed in a steering force transmission path transmitting a steering force applied to the steering handle to the propeller, wherein the steering assist apparatus is arranged in an intermediate portion of a steering cable constituting the propelling force transmission path.
 2. The power steering apparatus of a watercraft with propeller as claimed in claim 1, wherein the steering assist apparatus is arranged in a gunwale side of the center of the hull.
 3. The power steering apparatus of a watercraft with propeller as claimed in claim 1, wherein the steering assist apparatus is provided with a torque sensor detecting a steering torque applied to the steering handle, a control unit controlling the steering assist apparatus, and a motor assisting the steering operation within a gear case.
 4. The power steering apparatus of a watercraft with propeller as claimed in claim 2, wherein the steering assist apparatus is provided with a torque sensor detecting a steering torque applied to the steering handle, a control unit controlling the steering assist apparatus, and a motor assisting the steering operation within a gear case.
 5. The power steering apparatus of a watercraft with propeller as claimed in claim 1, wherein an output side of the steering assist apparatus is provided with a screw reaction force suppressing apparatus setting up against an inverse input applied to the steering cable from a side of the propeller on the basis of a rotational reaction force of a screw provided in the propeller.
 6. The power steering apparatus of a watercraft with propeller as claimed in claim 2, wherein an output side of the steering assist apparatus is provided with a screw reaction force suppressing apparatus setting up against an inverse input applied to the steering cable from a side of the propeller on the basis of a rotational reaction force of a screw provided in the propeller.
 7. The power steering apparatus of a watercraft with propeller as claimed in claim 3, wherein an output side of the steering assist apparatus is provided with a screw reaction force suppressing apparatus setting up against an inverse input applied to the steering cable from a side of the propeller on the basis of a rotational reaction force of a screw provided in the propeller.
 8. The power steering apparatus of a watercraft with propeller as claimed in claim 4, wherein an output side of the steering assist apparatus is provided with a screw reaction force suppressing apparatus setting up against an inverse input applied to the steering cable from a side of the propeller on the basis of a rotational reaction force of a screw provided in the propeller.
 9. A power steering apparatus of a watercraft with propeller as claimed in claim 5, wherein the steering assist apparatus coaxially couples an input shaft and an output shaft via a torsion bar, and pivots the input shaft and the output shaft to the gear case, and wherein the screw reaction force suppressing apparatus is constructed by a braking means applying a constant braking force to the output shaft.
 10. A power steering apparatus of a watercraft with propeller as claimed in claim 6, wherein the steering assist apparatus coaxially couples an input shaft and an output shaft via a torsion bar, and pivots the input shaft and the output shaft to the gear case, and wherein the screw reaction force suppressing apparatus is constructed by a braking means applying a constant braking force to the output shaft.
 11. A power steering apparatus of a watercraft with propeller as claimed in claim 7, wherein the steering assist apparatus coaxially couples an input shaft and an output shaft via a torsion bar, and pivots the input shaft and the output shaft to the gear case, and wherein the screw reaction force suppressing apparatus is constructed by a braking means applying a constant braking force to the output shaft.
 12. A power steering apparatus of a watercraft with propeller as claimed in claim 8, wherein the steering assist apparatus coaxially couples an input shaft and an output shaft via a torsion bar, and pivots the input shaft and the output shaft to the gear case, and wherein the screw reaction force suppressing apparatus is constructed by a braking means applying a constant braking force to the output shaft.
 13. A power steering apparatus of a watercraft with propeller as claimed in claim 5, wherein the screw reaction force suppressing apparatus is constructed by an input side member to which a motor torque of an electric assist motor is input, an output side member from which the motor torque is output, and a static side member in which a rotation is constrained, and comprises a lock means which is provided between the static side member and the output side member and locks the output side member and the static side member with respect to an inverse input torque from the output side member, an unlocking means which is provided in the input side member and unlocks the lock state by the lock means with respect to the motor torque from the input side member, and a torque transmitting means which is provided between the input side member and the output side member and transmits the motor torque from the input side member to the output side member at a time when the lock state by the lock means is unlocked.
 14. A power steering apparatus of a watercraft with propeller as claimed in claim 6, wherein the screw reaction force suppressing apparatus is constructed by an input side member to which a motor torque of an electric assist motor is input, an output side member from which the motor torque is output, and a static side member in which a rotation is constrained, and comprises a lock means which is provided between the static side member and the output side member and locks the output side member and the static side member with respect to an inverse input torque from the output side member, an unlocking means which is provided in the input side member and unlocks the lock state by the lock means with respect to the motor torque from the input side member, and a torque transmitting means which is provided between the input side member and the output side member and transmits the motor torque from the input side member to the output side member at a time when the lock state by the lock means is unlocked.
 15. A power steering apparatus of a watercraft with propeller as claimed in claim 7, wherein the screw reaction force suppressing apparatus is constructed by an input side member to which a motor torque of an electric assist motor is input, an output side member from which the motor torque is output, and a static side member in which a rotation is constrained, and comprises a lock means which is provided between the static side member and the output side member and locks the output side member and the static side member with respect to an inverse input torque from the output side member, an unlocking means which is provided in the input side member and unlocks the lock state by the lock means with respect to the motor torque from the input side member, and a torque transmitting means which is provided between the input side member and the output side member and transmits the motor torque from the input side member to the output side member at a time when the lock state by the lock means is unlocked.
 16. A power steering apparatus of a watercraft with propeller as claimed in claim 8, wherein the screw reaction force suppressing apparatus is constructed by an input side member to which a motor torque of an electric assist motor is input, an output side member from which the motor torque is output, and a static side member in which a rotation is constrained, and comprises a lock means which is provided between the static side member and the output side member and locks the output side member and the static side member with respect to an inverse input torque from the output side member, an unlocking means which is provided in the input side member and unlocks the lock state by the lock means with respect to the motor torque from the input side member, and a torque transmitting means which is provided between the input side member and the output side member and transmits the motor torque from the input side member to the output side member at a time when the lock state by the lock means is unlocked. 